Rocket propulsion method



July 28,1959

A. ZLETZ ETAL 2,896,406

ROCKET PROPULSION METHOD Filed Feb. 16, 1953 OX/DIZER I INVENTORS: Alex Z/efz y Dan 1?. Carmqdy ATTORNEY United States Patent 2,896,406 ROCKET PROPULSION METHOD Application February 16, 1953, Serial No. 336,909 19 Claims. 9 (Cl. 60--35.4)

This invention relates to the generation of gas. More particularly, it relates to reaction propulsion by the hypergolic reaction of a liquid fuel and a liquid oxidizer. Still more particularly, the invention relates to a method of rocket propulsion by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer, which materials spontaneously react to generate gas at high pressure and high temperature.

' Reaction propulsion is now being used for many aerial purposes. For many uses it is necessary to operate with a fuel system which is not dependent on atmospheric oxygen. This fuel system may consist of a single selfcontained propellant or it may consist of a separate fuel and a separate oxidizer, i.e., a bipropellant system.

In the bipropellant system the fuel and the oxidizer are introduced separately and essentially simultaneously into the combustion chamber of the reaction motor. The products of oxidation from the reaction of the fuel and the oxidizer are discharged through an orifice at the exit end of the combustion chamber and thereby produce the driving force. Because of the possibilities of electrical and/or mechanical failure of the auxiliary methods of ignition such as a spark or a hot surface, it is preferred to use a self-igniting fuel system. A fuel which is selfigniting, i. e., spontaneously combustible when contacted with an oxidizer, is known as a hypergolic fuel.

Temperature has an important effect on the hypergolic activity of fuels. The temperature at the earths surface may vary from a high of about +125 F. to a low of as much as 65 F.; in general temperatures below about 20 or 30 F. are exceptional. Thus surface-to-air missiles or rocket-driven aircraft should be capable of operation when the temperature of the fuel and the oxidizer at the moment of initial contact in the combustion chamber of the rocket motor is on the order of -20 F. Temperatures at high altitudes are frequently on the order of 65 F. and are known to approach 100 F. Thus an air-to-air missile should be able to operate satisfactorily when the temperature of the fuel and the oxidizer at the moment of initial contact in the combustion chamber is on the order of -'65f F.

The more common oxidizers are white fuming nitric.

acid, red fuming nitric acid and nitric acid-sulfuric acid mixtures. While these nitric acid oxidizers operate satisfactorily over a Wide range of atmospheric temperatures they have important drawbacks. The nitric acid oxidizers are extremely corrosive; they have poor storage stability; they give oif toxic gases; and special precautions must be taken by personnel who handle these oxidizers.

Concentrated aqueous hydrogen peroxide solutions have excellent storage stability and do not give off harmful gas. However, these aqueous hydrogen peroxide solutions such as 90% hydrogen peroxide have the disadvantage of comparatively high freezing-points, e.g., 90% hydrogen peroxide solution freezes at -+l2 F. The freezing point of 80% hydrogen peroxide is 9 F., but the activity of this solution toward the prior art fuels is markedly lower than the 90% H 0 solution. The freezing point of aqueous hydrogen peroxide solutions can be depressed by dissolving therein inorganic salts, preferably ammonium nitrate. Thus a solution containing 40 weight percent of ammonium nitrate and in which the hydrogen peroxide-water portion contains 90 weight percent of H 0 has a freezing point of about --30 F. A so-called H O -30% NH NO solution has a freezing point of below 70 F.

Concentrated aqueous hydrogen peroxide solutions have been used as monopropellants by cat-alytically decomposing the hydrogen peroxideusing such catalysts as potassium permangante or copper oxide. Since the decomposition products contain free-oxygen the monopropellant system is inefficient. However, fuels which are hypergolic with nitric acid oxidizers may be much less active or even inactive with concentrated H 0 solutions. Anhydrous hydrazine is usually considered to be the only fuel that is sufficiently hypergolic with concentrated H 0 solutions to be practical; however, bydrazine has the disability of a comparatively high freezing point. in the presence of a H 0 decomposition catalyst. Furthermore, the prior art fuels are less effective with arm monium nitrate containing aqueous hydrogen peroxide than with aqueous hydrogen peroxide alone.

An object of this invention is a method of generating gas by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer. Another object is a method of reaction propulsion by the hypergolic interaction of a fuel and a hydrogen peroxide oxidizer. Still another object is a method of reaction propulsion by the hypergolic interaction of a hydrogen peroxide oxidizer and a fuel which contains appreciable amounts of hydrocarbons, particularly non-hypergolic liquid hydrocarbons. -A particular object is a method of generating gas by the hypergolic interaction of a defined fuel and an oxidizer consisting of an aqueous hydrogen peroxide solution containing dissolved ammonium nitrate. Another particular object is a method of rocket propulsion by the hypergolic interaction of a defined organic halothiopihosphite and a defined hydrogen peroxide oxidizer when the temperature of the fuel and the oxidizer is above about 20 F. Other objects will become apparent in the course of the detailed description of the invention.

A method has been discovered for generating. gas, which gas may be used as a substitute for compressed air for certain purposes or for driving the turbine of a jet engine or for rocket propulsion, which method comprises contacting (1) A hypergolic fuel consisting essentially of a halothi0' the halogen radical is selected from the class consisting of chlorine and bromine, and (2) An oxidizer selected from the class consisting of (a) Aqueous hydrogen peroxide solutions which;

contain at least about 80 weight percent of H 0 and the remainder is essentially water and (b) Aqueous hydrogen. peroxide-inorganic salt solutionswherein the hydrogen. peroxide water portion contains at least about 80 weight percent A mixed fuel made up of methylhalothiophosphitewhich contains as much as 40 volume percent of miscible;

hydrocarbon is hypergolic with aqueous hydrogen per- -Pattented July 28, 1959' Some fuelsare operative with H 0 solutions oxide am'monium nitrate solutions containing at least about90 weight percent of hydrogen peroxide in the H O -water portion when the fuel and the oxidizer are ata temperatureof about +60 F. The lower the temperatureof initial contact the less hydrocarbon tolerable inithemixe'd fuel.

'ICertai'n'brganic halothiophosphites ignite spontaneously 'when'contacted with hydrogen peroxide oxidizers. The various halothiophosphites do not'have equal hypergolic activity with the same oxidizer. However, "by proper selection .of the'halothiophosphite, it is possible to obtain a hypergolic reaction with a tolerable ignition delay when the halothiophosphite and the oxidizerare at a temperature of about 20 F. at the moment of initial contact in the gas generating chamber.

TTheseorganic halothiophosphites have the generic empirical formula (RS),,PX where P represents the element phosphorus, S represents the-element sulfur, X represents a halogen radical selected from the class .con sisting of c hlorine and bromine, and R represents an aliphatic hydrocarbon radical, and wherein a is 1 or 2, b is l or 2 and the sum of a and b is 3.

The halothiophosphites which are suitable for the purposes of this invention contain aliphatic hydrocarbon radicals which may be paraflinic, e.g.,-methyl, ethyl,iso

propyl and n-propyl; or olefinic, e.g., ethenyl, propenyl,

isopropenyl, or acetylenic, e.g., ethinyl and propinyl; or cycloalkyl or cycloalkenyl, e.g., cyclopropyl and cyclopropenyl. In the case of the aliphaticdihalothiophosphites, the total number of carbon atoms should be not more than 6; While in the case of the dialiphatichalothiophosphites, the total number of carbon atoms shoul'd be not more than 8 and not more than 6 carbon atoms should be present in any one aliphatic radical.

The most suitable halothiophosphites for the purposes of this invention are the alkylhalothiophosphites wherein the alkyl radicals are selected from the group consisting of methyl, ethyl and mixtures thereof. For operation where the halothiophosphite and the oxidizerwill be at a temperature of about 20 F. at the moment of initial contacting of the halothiophosphite and the'oxidizer, the preferred halothiophosphites are the methylhalothiophosphites.

A mixed fuel which is suitable for the generation of gas can be made by mixing aliphatichalothiophosphitcs with miscible hydrocarbons. The minimum amountof halothiophosphite necessarily present in said hypergolic mixed fuel will vary with the type of hydrocarbon, the desired temperature of operation and the type of H oxidizer. For example: As much as 40% of a petroleum fraction is tolerable in a hydrocarbon-methyldichlorothiophosphite blend which must be hypergolic at about +60 F. when using an ammonium nitrate containing 90% hydrogen peroxide oxidizer. In general petroleum hydrocarbon fractions are suitable materials as for example those fractions boiling between about 300 and 600 F. which correspond to the fuel requirement of military jet engines. Aromatic hydrocarbons which boil below about 600 F. are suitablehydrocarbons for this purpose. The hypergolic activity of the mixed fuel can be improved at lower atmospherictemperatures by using as the hydrocarbon component olefinic hydrocarbons such as thermally cracked naphthas and gas oils or turpentine. Conversely, at higher atmospheric temperatures a hypergolic mixed fuel containing less halothiophosphite is obtainable by the use of unsaturated hydrocarbons.

The oxidizers of this invention are either concentrated aqueous hydrogen peroxide solutions or aqueoushydrogen peroxide solutions containing dissolved inorganic salts, for example, ammonium halides, sodium sulfate, sodium nitrate, etc.; for low temperature operationrequiring a short ignition delay, ammonium nitrate must be used .as the salt. The concentrated aqueous hydrogen peroxide solutions should contain at least about 80 weight, percent of H 0 the remainder of the solution is essentially water.

The hypergolic activity of: the aqueous hydrogen peroxide solution is improved by increasing the concentration of the peroxide. Commercially available 90% H 0 solution is an excellent oxidizer for operation above 0 F. For low temperature operation it is preferred to use aqueous H O -ammonium nitrate solutions, such as 90%--40% or"%30%" solutions. 7

Concentrated laqueous hydrogenperoxide solution as made commercially is virtually 'only H 0 and water. In order to improve storage stability smallamounts of stabilizers are commonly added to the solution, e.g., sodium stannate, tetrasodium pyrophosphate, adipic acid, tartaric acid; in general only trace amounts of stabilizers are added so that the solution consists essentially of hydrogen peroxide and water.

In order --to depress the freezing point of aqueous hydrogen peroxide solutions soluble inorganic salts are dissolvedtherein, e.g., sodium nitrate, potassium. nitrate and ammonium nitrate have been used. These saltcontaining solutions are commonly designated in terms of the weight percent of salt in the total solution and the weight percent of hydrogen peroxide. present in the aqueous portion of the solution, e.g., H O 40% NH NO indicates that thetotal aqueous hydrogen peroxide-nitrate solution consists of 40 weight percent of ammonium nitrate and 60 weight percent of aqueous hydrogen peroxide composed of 90 weight percent of H 0 and the remainder essentially water. This particular solution has a freezing point of 30 F. A temperature of 70 F. is attainable with -an 80% H O 30% NH NO solution. It is preferred to operate in the presence of ammonium nitrate because of the pronounced favorable effect on the hypergolic activity of the fuels of this invention.

It has previously been found that trithiophosphites having the empirical formula RRR"S P where R, R and R represent aliphatic hydrocarbon radicals containing from '1 to 3 carbon atoms and the total number of:carbonatoms in the molecule is between 3 and 7 are hypergolic with the above defined H 0 oxidizers at temperatures above aboutO" F. Examples ofthese fuels are trimethyltrithiophosphite and triethyltrithiophosphite. The hypergolic activity of these fuels at lower temperatures can be greatly improved by addingthereto small amounts of the above defined halothiophosphites, i.e., the halothiophosphites have a synergistic catalytic-effect on the activity of the aliphaticthiophosphites. For low tempera tures thehalothiophosphite-thiophosphite fuel shouldcontain between about 1 and 20 volume percent of the halothiophosphite.

Ethylchlorothiophosphite was prepared by the method of Claesson, 'l-Prakt. Chem. (2), 15, 211 (1877), as follows: Phosphorustrichloride (-1 mol) was introduced into a 3-necked flask along with ml. of CHCl Ethyl mercaptan (1.38 mols) was added atO" C. The reaction mixture was heated to about 18 C. and the temperature raised to 50 C. over a time of one hour. The OHCl was'distilled and the product was carefully fractionated through -a Vigreaux column about .5 inches tall at about 18 mm. :Hg pressure. Two essentially pure products were obtained: ethyldichlorothiophosphite, boiling at 77 C. at 18 mm. Hg and diethylchlorodithiophosphite, boiling at 114 C. at l8 mm.Hg.

The ignition characteristics of various fuels were studied using a drop test. This method utilizes a test tube, 1 in. x 4 in., containing about 0.5 ml. of oxidizer. The "fuel to be tested was drawn into a hypodermic syringe. It was then ejected forcibly against the oxidizer surface by depressing thesyringe plunger. By this method amounts offuel of 'as'little as 0.01 mlacan be added. Low temperature tests were carried out by cooling the test tube'and the-oxidizer 'contained therein by means of abathpa drying tube inserted intothe top of the test tube excluded moisture. separately to the desired test temperature. By supercooling it was possible to carry out tests at temperatures below the freezing point of the fuel and/ or the oxidizer.

The ignition delay, which is the time elapsing between the addition of fuel to the oxidizer and visual ignition thereof, was determined as either (a) very short which corresponds to substantially instantaneous ignition, (b) short, which corresponds to substantially less than 1 second, and (c) more than 1 second, which time was determined by a stop watch.

'The following tests illustrate the activity of the halothiophosphites of this invention and hydrazine with hydrogen peroxide oxidizers.

Test 1 I In order to observe the effectiveness of ethylchlorothiophosphites with oxidizers consisting of aqueous hy* drogen peroxide and aqueous hydrogen peroxide-am monium nitrate solutions, several runs were made at var ious temperatures using 0.5 ml. of oxidizer.

For comparative purposes hydrazine was contacted at various temperatures with various H solutions as the oxidizer.

H 0 Fuel Temp., Run N o. oxidizer, I added, F. Igmtion delay percent ml.

90 0.05 +70 Very short. 80 0. 03 +70 Short. 80 0.10 +14 No ignition (efifervescence).

90-40 0 03 +14 N0 ignition.

90 0 03 +14 Very short.

Test III The hypergolic activity of a mixture of thiophosphite and halothiophosphitc was tested. Triethyltrithiophosphite prepared by reacting PCl and ethyl mercaptau was fractionated under conditions such that a trace amount of chlorine remained therein; believed to be diethyl chlorodithiophosphite. The activity of this mixture was compared with chlorine-free triethyltrithiophosphite.

H 0 Fuel Temp., Run No. Fuel oxidizer, added, F. Ignition delay percent m1.

Pure- 90 0. 05 +70 No ignition. 13- do 90 0.06 +70 77 sec. 14- do 90 0. 08 +70 22 sec. 15- Mixed 90 0. 05 +70 18 sec. 16-- .-d0 90 0. 08 +70 13 sec.

T-hese runs show the favorable eifect on ignition delay of a trace amount of the halo derivative on the activity of the trithiophosphite.

It is obvious from the data presented above that this invention can be used to generate gas at high pressure. This gas can be used for operating machinery such as compressed air hammers or for aircraft catapults; an-.

other important use for this high pressure gas is in the starting of the turbines of jet-type engines. The inven- The fuel was cooled '6 tion is particularly useful in aerial missiles which require a compact power plant that develops large amounts of energy over a very short period of time. Other examples of the use of this invention are: the rocket-assisted takeoff or flight of aircraft; aerial missiles; boosters for surface vehicles.

The relative proportion of oxidizer-to-fuel used will depend upon the type of operation, the temperature of .operation and the type of fuel and oxidizer being used. When using a %-40% hydrogen peroxide-ammonium nitrate solution as the oxidizer and methyldichlorothiophosphite as the fuel, between about 4 and 5 volumes of oxidizer are needed per volume of fuel.

By way of example this invention is applied to the propulsion of a surface-to-air missile. The annexed figure which forms a part of this specification shows schematically the bipropellant feed system and the motor of this missile. This missile is suitable for operations wherein the fuel and the oxidizer can be maintained at a temperature high enough to insure at least a shout ignition delay, e.g., when using ammonium nitrate containing H 0 solution as the oxidizer and methyldich-lorothiophosphite as the fuel, a temperature of about 20 F.

In the drawing vessel 11 contains a quantity of gas at high pressure; this gas must be inert with respect to the oxidizer and the fuel; suitable gases are nitrogen and helium. Herein helium is used as the inert gas. Helium from vessel 11 is passed through line 12 and through valve 13 which regulates the flow of gas to maintain a constant pressure beyond valve 13. From valve 13 heliurn is passed through lines 14- and 16 into vessel 17 and simultaneously through line 18 into vessel 19.

Vessel 17 contains the oxidizer. Helium pressure forces the oxidizer out of vessel 17 through line 21 to valve 22. Valve 22 is a solenoid actuated throttling valve. Suitable electrical lines connect valve 22 to an electrical source and operating switch (not shown) at the control chamber at the launching site. The oxidizer is passed through line 23 and injector 24 into combustion chamber 26. Combustion chamber 26 is provided with an outlet nozzle 27.

Vessel 19 contains the fuel. Vessels 17 and 19 are constructed to withstand the high pressure imposed by the helium gas. The gas pressure forces fuel from vessel 19 through line 28 to solenoid actuated throttling valve 29. Valve 29 is similar in construction and in actuation to valve 22. The fuel is passed through line 31 and injector 32 into combustion chamber 26.

Valves 22 and 29 are of such a size and setting that a predetermined ratio of oxidizer-to-fuel is passed into combustion chamber 26. Injectors 24 and 32 are so arranged that the streams of oxidizer and fuel converge and contact each other forcibly, resulting in a very thorough intermingling of the fuel and the oxidizer.

The missile is launched by activating the solenoids on valves 22 and 29. In this example 4.5 volumes of oxidizer per volume of fuel is introduced into the combustion chamber. The oxidizer and the fuel react almost instantaneously upon contact in the combustion chamber; a large volume of very hot gas is produced in the combustion chamber, which gas escapes through orifice 27. The reaction from this expulsion of gas drives the missile toward its target.

Thus having described the invention, what is claimed 1. A method of generating gas, which method comprises injecting separately and essentially simultaneously into the combustion chamber of the gas generator (1) a hypergolic fuel consisting essentially of a member selected from the class consisting of (i) organicdihalothiophosphites containing not more than 6 carbon atoms and (ii) diorganichalodithiophosphites containing not more than 8 carbon atoms and not more than 6 carbon atoms in an organic group, wherein the organic group in (i) and (ii) above are aliphatic and the halogen radicals are selected frornztheclass consisting of chlorine and bromine and (2) an coxidizer selected from the class consisting of 1) aqueousihydrogen peroxide solutions consisting of ati least 4. The method of claim'l wherein said fuel is diethylchlorodithiophosphite. I

5, The method of claim 1 wherein said fuel is ethyldi chlorothiophosphite. I I I 6. The method of claim 1 wherein said oxidizer con sists of about 80 weight percentwof H 0 and the remainder essentially Water. I I

7. The method of claim 1 wherein said oxidizer con sists of about 90 Weight percent oqf'H o and the remainder essentially water, r t

8. Themethod'of claim 1 wherein said oxidizer consists of a'solution of hydrogenperoxide, water andzammonium nitrate, wherein the nitrate content is about weight percent and the hydrogen;-peroxide-water portion 'consistsofabout-80 weight percent of H 0 .and the re maincler essentially water.

,9. The method of claim 1 wherein said oxidizer con sists of a solution of hydrogen peroxide, water and am monium nitrate, wherein the nitrate content is about 40 weight percent and the hydrogen peroxide-water portion consists of about 90 weight'percent of H 0 andithe remainder essentially water. i

10. A method of generating gas, which method comprisesinjccting separately and essentially simultaneously into the combustion chamber of the gas generator (1) a hypergolic mixed fuel consisting essentially of (I) a liquid miscible hydrocarbon and (Ii) methyldicl'ilorothiophos phite -and (2) an oxidizer selected fronrthe class con sisting of (0) aqueous hydrogen peroxide solutions consisting of at least about 80 weightipercent OfH O and the remainder essentially water, and (b) aqueous hydrogen i peroxide-ammonium nitrate solutions wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H O and the remainder essentially water, in an amount and at a rate suflicient to initiate a hypergolic reaction with and to support combustion of the :mixed fuel.

11. The method ofclaim 10 wherein said hydrocarbon is a liquid petroleum fraction boiling between about 300 and about 600 F.

12. The method of claim 10 wherein said hydrocarbon is a liquid aromatic hydrocarbon boiling below about 600 F.

'13. The method of claim 10 whereinsaid hydrocarhon is'a liquid olefin boiling below about-600 F. 1 4., A method of generating gas, which method comprises injecting separately and essentially simultaneously into 'the combustion chamber of =the gas genevator: ('1) a hypergolicmixed fuel consisting :cssentiallymf ('I) a liquid miscible hydrocarbon and ('II) ethyldichlorothiophosphite andtl} an oxidizer-selected from the class consisting-of (a) aqueous hydrogen peroxide solutions consisting 'of at' least about 80 -weight percentof H 0 and the remainder essentially Water, "and (b) aqueous hydrogen peroxide-ammonium 1 nitrate solutions" wherein the hydrogen r peroxide-wateruportion is the-predominant component'and consists of at .leastrabout '80rweigbtgper cent of H 0 and the remainder essentially water, in an amount and at a rate sufiicient to initiate a ,hypergolic reaction with and r to supportcombustion of the mixed fuel.

l5. A-methoduof gas generation, which method comprises injecting separately and essentiallysimultaneously 7 into the combustion chamber ofithe, gas generator ('1 a hypcrgolic tuel 'consisting -essentially"of (A) trialkyltrithiophosphitesrwhereinthealkyl radicals contain from,

1 110 3 carbon atoms and thetotal number of carbon atoms in the trithiophosphite 'is from 3 to 7 and (B) between aboutl and-about 20--volume 'percent'based on-fuel of a halothiophosphite selected from the tclasstconsisting .of (i) organic dihalothiophosphitesi'containing not more than 6 carbon atoms and (ii) idiorganic'halodithiophosphites containing not more than-8 carboniatoms: and not more than-6 carbon atoms in anrorganic group, wherein the organic groups in (i) and (ii)'- above are-aliphatic and the halogen radicals are selected from the class con- 1 sisting of chlorine and'brornineand (2) an oxidizer seiected from the class consisting of (a) aqueous hydrogen peroxide solutions consistingof at least-'about'iiit) weight 7 percent. oil-I 0 and the remainder essentially Water and ([7) aqueous hydrogen peroxide-ammonium nitrate solutions, wherein the hydrogen peroxide'water portion is the predominant component and COI'ISiStSIOf at least about '80 weightupercent of H 0 and the remaindenessentiaily References Cited in thefile of this patent FOREIGN PATENTS Switzerland 1May'2, 1949 OTHER REFERENCES Claessonfl]. Prakt. iChem.,rvo1. 15 (1877), page 211. 

1. A METHOD OF GENERATING GAS, WHICH METHOD COMPRISES INJECTING SEPARATELY AND ESSENTIALLY SIMULTANEOUSLY INTO THE COMBUSTION CHAMBER OF THE GAS GENERATOR (1) A HYPERGOLIC FUEL CONSISTING ESSENTIALLY OF A MEMBER SELECTED FROM THE CLASS CONSISTING OF (I) ORGANICDIHALOTHIOPHOSPHITES CONTAINING NOT MORE THAN 6 CARBON ATOMS AND (II) DIORGANICHALODITHIOPHOSPHITES CONTAINING NOT MORE THAN 8 CARBON ATOMS AND NOT MORE THAN 6 CARBON ATOMS IN AN ORGANIC GROUP, WHEREIN THE ORGANIC GROUP IN (I) AND (II) ABOVE ARE ALIPHATIC AND THE HALOGEN RADICALS ARE SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE AND (2) AN OXIDIZER SELECTED FROM THE CLASS CONSISTING OF (A) AQUEOUS HYDROGEN PEROXIDE SOLUTIONS CONSISTING OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER AND (B) AQUEOUS HYDROGEN PEROXIDEAMMONIUM NITRATE SOLUTIONS WHEREIN THE HYDROGEN PEROXIDE-WATER PORTION IS THE PREDOMINANT COMPONENT AND CONSISTS OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER, IN AN AMOUNT AND AT A RATE SUFFICIENT TO INITIATE A HYPERGOLIC REACTION WITH AND TO SUPPORT COMBUSTION OF THE FUEL. 